1. Field of the Invention
The present invention relates to a packet transfer apparatus and a packet transfer method.
2. Description of the Related Art
When data is transmitted to a receiver terminal via a network, the data is divided into packets, relayed by a communication apparatus, and delivered to the receiver terminal. Such communication apparatus that relays packets include a layer 2 switch.
Japanese Patent Application Laid-open No. 2006-203735 discloses a conventional technology using link aggregation to improve the quality of a communication link between network elements. Link aggregation is the ability to group a plurality of physical links, such as cables, between network elements into a single virtual physical link.
By the link aggregation, a high-speed communication link can be realized without an expensive cable or communication interface. Besides, a plurality of physical links are used together as a single link, even if part of the physical links fail, the communication link can be prevented from being cut completely, which improves the usability of the communication link.
When packets are transferred by using a link aggregation, one packet is transferred by only one of physical links. In the network including a plurality of communication apparatuses such as layer 2 switches, link trace can be performed to check the connectivity, i.e., connection path, between these communication apparatuses.
The layer 2 switch can constitute a network having a redundant path by a spanning-tree protocol. The link-trace function also enables easy collection of new path information when a path is switched from one to another in the network having such a configuration.
In the conventional technology, however, when communication apparatuses are connected with each other by a link aggregation, a link-trace packet is transferred through only one physical link. Accordingly, it cannot be determined whether packets are transferred without error in all physical links constituting the link aggregation.
Therefore, there is a need of a technology for determining whether packets are transferred without error in all physical links constituting a link aggregation (each physical link in a trunk) using a link-trace packet.